Specular reflectance photometric detection of cortical displacement

A non-contacting photometric displacement detector was described and used to measure cortical surface displacements. The variation in the proportion of a specular reflected parallel light beam incident on a photoconductive cell with vertical displacement of the reflective surface provides an accurate method of measuring small displacements of the cortical surface. Cortical surface displacements are always associated with alterations in systemic blood pressure. Pyramidal tract stimulation, barbiturate administration and Metrazol administration alter systemic blood pressure and cause concurrent cortical surface displacement. The problems caused by surface curvature, alteration in surface curvature, diffuse reflection and alteration in the spectral composition of diffuse reflected light by absorption are discussed. Advantages include probeless and inertialess operation, precise measurement of displacement of a discrete surface area and ease of calibration.